Hysteresis Correction for Capacitive Pressure Sensors
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Solution Overview
Problem
Existing correction methods for electrostatic capacitance type pressure sensors are limited in addressing hysteresis errors with nonlinear characteristics, as they are primarily designed for linear load changes and cannot effectively correct errors during both load increase and decrease phases.
Innovation Solution
A correction device and method that utilize specific functions fPEAK and fHYS to generate correction values for electrostatic capacitance during load decrease, reducing arithmetic processing load by not generating correction values for load increase, and using these functions to accurately detect designated loads with simple arithmetic operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If proportional calculation using turning point of actually applied load is used to correct hysteresis error, then correction can be applied to linear load sensors, but the correction method cannot handle nonlinear hysteresis characteristics where maximum value has nonlinear relationship with load change
Solution Approach 1:
The patent introduces two functions: fPEAK(FX) that generates maximum hysteresis correction values based on ultimate load, and fHYS(FN/FX×FMAX) that generates hysteresis correction values based on applied load ratios. These functions transform the nonlinear hysteresis characteristics into correctable parameters, enabling accurate correction for nonlinear load sensor behavior while maintaining computational efficiency.
2Measurement precision
If correction values are generated for both load increase and load decrease phases, then complete hysteresis correction is achieved, but arithmetic processing load increases
Solution Approach 1:
The patent inverts the correction approach by only generating correction values for load decrease phases rather than both increase and decrease phases. The correction value generation unit calculates correction values based on ultimate load and applied load ratio, which are then applied during load decrease. This inversion reduces arithmetic processing load while maintaining effective hysteresis correction.
3Measurement precision
If original gradually increasing and gradually decreasing hysteresis characteristics are used for correction, then linear load sensors can be corrected, but nonlinear hysteresis characteristics cannot be effectively addressed
Solution Approach 1:
The patent transforms the hysteresis correction approach by introducing functions that operate on ultimate load and applied load ratio rather than using original gradually increasing and decreasing characteristics. The function fPEAK(FX) processes ultimate load to generate maximum correction values, while fHYS(FN/FX×FMAX) processes load ratios to generate appropriate correction values for different operating conditions. This parameter transformation enables reliable correction of nonlinear hysteresis characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively corrects hysteresis errors with nonlinear characteristics by subtracting correction values from the electrostatic capacitance during load decrease, reducing processing load and ensuring accurate detection of applied loads, thereby addressing the limitations of existing technologies.
Implementation Method 1
an electrostatic capacitance type pressure sensor having hysteresis characteristics in which an error in a read value of electrostatic capacitance changes
Implementation Method 2
electrostatic capacitance type pressure sensor
Implementation Method 3
hysteresis characteristics in which an error in a read value of electrostatic capacitance changes depending on a maximum ultimate load of an applied load
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
A correction device includes a specification unit which specifies an ultimate load FX at the time of an increase in applied load, a correction value generation unit which generates a correction value for electrostatic capacitance actually read at the time of a decrease in load based on the ultimate load FX specified by the specification unit, a first function fPEAK(FX) for generating a maximum value of a hysteresis when the ultimate load FX is changed, and a second function fHYS (FN/FX×FMAX) for generating a hysteresis when a rated load FMAX of the electrostatic capacitance type pressure sensor is applied, and a correction unit which corrects electrostatic capacitance actually read at the time of a decrease in applied load using the correction value.